The invention relates to curtain-sided vehicles of the type having slidable doors attached to each end of a curtain. The curtain is used in conjunction with the doors, to close an open side of the vehicle. When the side of the vehicle is closed, each door engages an end of the vehicle by a hook or over center latch which causes the curtain to be pulled taut. When access is desired to the cargo area, the sliding door panels are unlatched and slid along the length of the trailer causing the curtain to relax and fold in a pleated manner. It is desirable to have the curtain fold into a compact position so that there is maximum access to the cargo area. An arrangement for causing the curtain to fold in a pleated manner is described in U.S. Pat. No. 4,545,611. The arrangement in the '611 patent uses biasing strips that urge a portion of the curtain away from the cargo area as the curtain pleats or folds. The biasing strips are described as strips of plastic material slightly curved to give the required bias. The biasing strips initially cause the curtain to fold outward from the cargo area. However, as the sliding doors are moved closer and closer together, the biasing strips operate to prevent the curtain from being completely folded in a compact position. If the sliding door and curtain are pushed into a compact position, the biasing strips exert a force tending to push the doors away from each other preventing maximum access to the cargo area. Reduced access to the cargo area limits the maximum load size and makes it more difficult to insert and move long loads into and from the cargo area.